Influence of bow shape and model scale on the natural transition in boundary layers on underwater axisymmetric bodies with a superhydrophobic surface

Abstract

This study uses numerical methods to investigate the influence of bow shape and model scale on the natural transition in bow boundary layers on underwater axisymmetric bodies with a superhydrophobic surface. The transition locations for eight bow shapes and four model scales are predicted by using the eN method, which is based on a linear stability theory. The results show that the superhydrophobic surface always stabilizes the boundary layer and delays the transition for different bow shapes and model scales. However, differences are observed in the basic laminar flow, boundary-layer stability, and transition location when different bow shapes are used. These differences are not prominent at the small model scale, but become significant at the medium and large model scales. As the model scale increases, the transition location in the boundary layer on the superhydrophobic surface moves upstream and then downstream, leading to a “dangerous” scale, at which the transition location is closest to the leading edge. Furthermore, this study provides the optimal bow shape with the latest transition location at each model scale, and the optimal bow shape with the longest transition delay distance.